Smog-eating tiles could reduce pollution

The American Lung Association's 2011 State of the Air Report states more than 154 million people in the U.S. suffer from pollution levels that often are too dangerous to breathe. Additionally, the World Health Organization recently estimated 2.4 million people worldwide die annually from causes directly attributed to air pollution.

A method has emerged that involves using titanium dioxide in roof tiles to reduce pollution and its effects. Titanium dioxide's depolluting capabilities reportedly have been successful in previous uses.

The Photocatalytic Innovative Coverings Applications for Depollution Assessment (PICADA) Project, which was conducted by a consortium of leading European contractors, manufacturers and research centers, demonstrates titanium dioxide's capabilities as a key ingredient in coatings to reduce pollution caused by nitrogen oxide and volatile organic compounds—the key ingredients of smog.

"In the studies conducted in Europe, where they actually applied titanium dioxide to roadways, the air was measurably cleaner," says Michael Chusid, president of Chusid Associates, Tarzana, Calif., a marketing and technical consultancy on building products. "It works."

Often formed in industrial processes and automobiles, nitrogen oxide is found in high concentrations in metropolitan regions where freeways are common. When activated by sunlight, smog-eating tile reportedly converts nitrogen oxide into calcium nitrates, which later are washed off the roof with rain and act as a ground soil fertilizer. According to studies conducted in Los Angeles by the Environmental Protection Agency, during one year, 2,000 square feet of smog-eating tiles can destroy about the same amount of nitrogen oxide that a car produces after being driven 10,800 miles.

According to Boral Roofing, titanium dioxide is a proven depollutant that occurs naturally and is safe for humans. The compound commonly is found in a number of items we interact with daily, such as paints, cosmetics, toothpaste and white roof membranes. It also is being used in hospitals on operating room walls for sterilization purposes.

"It is a stay-clean technology that can break down organic substances that commonly accumulate on roof surfaces," according to John Renowden, Boral Roofing's vice president of product development. "Substances such as mold and algae are destroyed when ultraviolet light hits the roof surface. The visible organic materials on the roof then become transparent, maintaining the appearance of the structure."

According to the Steep-slope Assembly Testing of Clay and Concrete Tile by Oak Ridge National Laboratory, Oak Ridge, Tenn., concrete tiles are an energy-efficient solution that helps homeowners achieve up to 22 percent in energy costs. Concrete tiles are made from locally sourced raw mineral materials—a mixture of sand, water and cement—and reportedly have the inherent energy benefits of high thermal mass, emissivity, reflectivity and an insulating air space between the tile and deck.